Field of the Invention
The present invention relates to a printing apparatus, a method of controlling the printing apparatus, and a storage medium, and more particularly to a printing apparatus to which a post-processing apparatus capable of performing a saddle-stitching process can be connected, a method of controlling the printing apparatus, and a storage medium.
Description of the Related Art
Conventionally, there has been known a post-processing apparatus that executes a saddle-stitching process for stitching (stapling) centers of a plurality of sheets, folding the stitched sheets into two, and outputs the sheets in the form of a brochure (see Japanese Patent Laid-Open Publication No. 2010-168134). In this post-processing apparatus, as shown in FIG. 25A, sheets conveyed from a printing apparatus (not shown) are discharged onto one of stacking trays 101 and 102 and a saddle-stitched product tray 103 according to a type of finishing process set by a user. For example, when no finishing process is to be executed, the sheets are discharged onto the stacking tray 101. When a normal stapling process is to be executed, the sheets are discharged onto the stacking tray 102, and when a saddle-stitching process is to be executed, the sheets are discharged onto the saddle-stitched product tray 103.
Further, in a saddle-stitching process section of the post-processing apparatus, there is a limit to the number of sheets which can be saddle-stitched due to restrictions on the apparatus. Conventionally, there has also been proposed an image processing apparatus that, when image data exceeding the limit of the number of sheets which can be saddle-stitched is input thereto, automatically changes a sheet discharge destination of a post-processing apparatus to thereby provide control such that the sheets are prevented from being conveyed to the saddle-stitching process section (see Japanese Patent Laid-Open Publication No. 2002-331730).
Further, in recent years, as shown in FIG. 25B, there has been proposed a post-processing apparatus that has attained downsizing of itself by using a common conveying path for executing a stapling process and for executing a saddle-stitching process. In this post-processing apparatus, in executing the saddle-stitching process, a sheet having entered the conveying path 104 for executing the stapling process is switched back by reverse rotation of a conveying roller pair 106, and is conveyed into a conveying path 105 for executing the saddle-stitching process. The post-processing apparatus employs a method of executing the saddle-stitching process on a plurality of sheets accumulated on an intermediate tray for executing the saddle-stitching process.
However, when a bookbinding process is executed using the post-processing apparatus shown in FIG. 25B, the saddle-stitching process is executed after switching back sheets having images printed thereon. Therefore, it is impossible to obtain a brochure in the correct page order if the order of image formation on sheets is the same as order of pages of the brochure.
Further, since a discharge destination of the sheets is different depending on whether or not the saddle-stitching process is designated, it is necessary to flexibly switch the order of image formation on the sheets during the bookbinding process according to the discharge destination. Therefore, when a sheet, such as thick paper having a large basis weight, which cannot be subjected to double-sided printing, is used as a cover of the brochure, the user is required to designate printing on the sheet while being conscious of whether an image is formed on a front side or a back side of the sheet, by taking a discharge destination of the sheet into account. This requires high-level operation skill of the user. Further, even if the user designates printing using his/her high-level operation skill, the user cannot always obtain a desired print product, because when image data is input which exceeds the limit of the number of sheets that can be saddle-stitched by the post-processing apparatus, the sheets are discharged onto a stacking tray which is not used for executing the saddle-stitching process.